The present invention relates to a waste water treatment material and sludge dehydrating agent containing, as an effective component thereof, sulfonated styrene polymer and its salt, and more particularly to a waste water treatment method and a sludge treatment method using the same.
Contamination of rivers, underground water and so forth caused from various industrial effluent, sewage sludge, excrement sludge have raised a critical social problem. Therefore, techniques for the waste water treatment have attracted keen interest.
Under the foregoing circumstances, a variety of waste water treatment techniques have been investigated. Flocculating treatment using a polymer flocculating agent is one of the foregoing techniques.
For example, in Japanese Patent Laid-Open No. 58-216707 and Japanese Patent Laid-Open No. 2-298400, a technique has been suggested which uses sodium-polystyrene sulfonate to serve as a waste water treatment material. According to the foregoing disclosures, an effect of flocculating the various waste water has been reported.
Available sodium polystyrene sulfonate, however, suffers from an unsatisfactorily small particle size of generated flocs, excessively low settling velocity and filtration velocity and unsatisfactory large water content in the dehydrated sludge (cakes) and turbidity of the filtered solution. From the foregoing viewpoint, the performance of the foregoing sodium polystyrene sulfonate is unsatisfactory.
On the other hand, treatment of sludge, such as sewage sludge, excrement sludge or various industrial waste water, has been performed by adding a flocculating agent (a dehydrating agent) to the sludge to flocculate suspended substances so as to produce flocs. Then, sludge from which the flocs have been obtained is dehydrated by a belt-press dehydrating machine or a filter-press dehydrating machine so as to separate the sludge into a solid component (a cake) and water. The foregoing sludge treatment must realize a low water content in the flocs and cakes produced in the foregoing process, a high filtration velocity required in the process for filtering sludge and a satisfactory separation characteristic between the filter cloth and the cakes.
As the dehydrating agent for use in the foregoing sludge treatment, cation polymer flocculating agent, such as polymer of quaternary salt of dinethylaminoethyl acrylate or dimethylaminoethyl methacrylate or copolymer of quaternary salt of dinethylaminoethyl acrylate or dimentylaimnoethyl methacrylate and acrylamide is solely employed. As an alternative to this, the cation polymer flocculating agent and an anion polymer flocculating agent are combined with each other.
A variety of polymers have been suggested as the anion polymer flocculating agent. For example, polyacrylic acid has been suggested in Japanese Patent Laid-Open No. 58-216707, while sodium polystyrene sulfonate having an average molecular weight of 1000 to 1,000,000 has been disclosed in Japanese Patent Laid-Open No. 2-298400.
However, sole use of the cation polymer flocculating agent suffers from a high water content of the produced flocs and, therefore, the realized dehydration characteristic is unsatisfactory. If the cation polymer flocculating agent and the anion polymer flocculating agent are combined with each other such that sodium polyacrylate or sodium polystyrene sulfonate having the average molecular weight of 1000 to 1,000,000 is employed as the anion type flocculating agent, there arises a problem of a low filtration velocity of sludge and an unsatisfactory processing efficiency.
An object of the present invention is to provide a novel waste water treatment material and a waste water treatment method with which settling velocity and filtration velocity can be raised and which are able to lower the water content in dehydrated sludge (cakes) and the turbidity of filtered solution.
Another object of the present invention is to provide a sludge dehydrating agent and a sludge treatment method with which the water content in the cakes produced in the process can be lowered, which enables a high filtration efficiency to be realized in a process for filtering sludge and which causes filter cloth and the cakes to easily be separated.
The inventors of the present invention have energetically performed investigations to obtain a waste water treatment material and a waste water treatment method which exhibit excellent settling velocity, filtration velocity, water content in dehydrated sludge, separability of dehydrated cakes and cleanliness (the turbidity) of filtered solution. Thus, the present invention has been achieved.
That is, a waste water treatment material according to the present invention comprises: sulfonated styrene polymer and/or its salt as an effective component thereof, wherein the sulfonated styrene polymer and/or its salt has a viscosity satisfying a range from 10 mPaxc2x7S to 20,000 mPaxc2x7S at 25xc2x0 C. after a neutral salt in a quantity which satisfies a range from 0.01 N to 5 N has been added to a 1 wt % water solution of the sulfonated styrene polymer and/or its salt.
A waste water treatment method according to the present invention comprising the steps of: adding a waste water treatment material containing sulfonated styrene polymer and/or its salt as an effective component to each of various waste water; and purifying waste water, wherein the sulfonated styrene polymer and/or its salt has viscosity satisfying a range from 10 mPaxc2x7S to 20,000 mPaxc2x7S at 25xc2x0 C. after neutral salt in quantity which satisfies a range from 0.01 N to 5 N has been added to 1 wt % water solution of the sulfonated styrene polymer and/or its salt.
The sulfonated styrene polymer and/or its salt having the above-mentioned characteristic exhibits a stable flocculating performance.
On the other hand, a sludge dehydrating agent comprises sulfonated styrene polymer and/or its salt having a weight average molecular weight of 1,100,000 or greater.
A sludge treatment method according to the present invention comprises the step of sequentially adding, to sludge, sulfonated styrene polymer having a weight average molecular weight of 1,100,000 or greater and/or its salt and cation polymer flocculating agent and/or inorganic flocculating agent.
The sulfonated styrene polymer having the weight average molecular weight of 1,100,000 or greater and/or its salt is employed as the sludge dehydrating agent. Moreover, the sludge dehydrating agent and cation polymer flocculating agent and/or inorganic flocculating agent are sequentially added to sludge. Thus, flocs each having a low water content are produced. When sludge from which the flocs have been produced is filtered, the filtering process can be performed at a high filtration velocity. Thus, sludge can be separated into filtrate having a low turbidity and sludge cakes. The thus-produced cakes can easily be separated from the filter cloth and have a low water content. As a result, fuel in a small quantity is required to burn the cakes. Thus, sludge treatment can efficiently be performed.
In an embodiment, the waste water treatment material of the present invention comprises a material selected from the group consisting of a sulfonated styrene polymer and a salt of a sulfonated styrene polymer, wherein a 1 wt % aqueous solution of said material has a viscosity ranging from 10 mPaxc2x7S to 20,000 mPaxc2x7S at 25xc2x0 C. after a neutral salt has been added to the aqueous solution so that a concentration of the neutral salt in the aqueous solution ranges from 0.01 N to 5 N.
In an embodiment, the viscosity of the aqueous solution ranges from 10 mPaxc2x7S to 500 mPaxc2x7S at 25xc2x0 C. after the neutral salt has been added to the aqueous solution so that a concentration of the neutral salt in the aqueous solution is about 0.2 N.
In an embodiment, the viscosity of the aqueous solution ranges from 10 mPaxc2x7S to 500 mPaxc2x7S at 25xc2x0 C. after the neutral salt has been added to the aqueous solution so that a concentration of the neutral salt in the aqueous solution is about 1 N.
In an embodiment, the sulfonated styrene polymer and/or its salt is water soluble and has a cross-linked structure.
In an embodiment, the sulfonated styrene polymer and/or its salt is sulfonated waste material.
In an embodiment, the waste water treatment method of the present invention comprises the steps of adding a waste water treatment material to waste water, the material being selected from the group consisting of a sulfonated styrene polymer and a salt of a sulfonated styrene polymer, wherein a 1 wt % aqueous solution of said material has a viscosity ranging from 10 mPaxc2x7S to 20,000 mPaxc2x7S at 25xc2x0 C. after a neutral salt has been added to the aqueous solution so that a concentration of the neutral salt in the aqueous solution ranges from 0.01 N to 5 N; and purifying the waste water.
In an embodiment, the material further comprises a flocculating agent selected from the group consisting of a nonionic polymer flocculating agent, an anionic polymer flocculating agent, a cationic polymer flocculating agent, and an inorganic flocculating agent.
In an embodiment, a material is selected from the group consisting of a sulfonated styrene polymer and a salt of a sulfonated styrene polymer, the sulfonated styrene polymer or the salt of the sulfonated styrene polymer having a molecular weight of at least 1,100,000.
In an embodiment, the sulfonated styrene polymer has a molecular weight ranging from 1,100,000 to 10,000,000.
In an embodiment, the sulfonated styrene polymer and/or its salt is prepared by cross-linking the sulfonated styrene polymer and/or its salt using a cross-linking monomer in an amount ranging from about 0.01 mol % to about 10 mol %.
In an embodiment, the sulfonated styrene polymer and/or its salt comprises a styrene polymer that has a pre-sulfonation average molecular weight ranging from 4.5 to 20.
In an embodiment, the method of dehydrating sludge comprises the steps of adding to the sludge a material selected from the group consisting of a sulfonated styrene polymer and a salt of a sulfonated styrene polymer; and adding a flocculating agent to the sludge and material, the flocculating agent being selected from the group consisting of a cationic polymer flocculating agent and an inorganic flocculating agent.